We kinda know this already
By BOSTON UNIVERSITY
These were the sort of questions Matthew Nayor and his team at
Boston University School of Medicine set out to answer in the largest study to
date aimed at understanding the relationship between regular physical activity
and a person’s physical fitness.
Their findings, which appear in the European Heart Journal, came from a study of
approximately 2,000 participants from the Framingham Heart Study. They found
that bouts of moderate to vigorous exercise—working out with more intensity
than, say, walking 10,000 steps over the course of a day—drastically improved a
person’s fitness, compared to milder forms of exercise.
“By establishing the relationship between different forms of habitual physical activity and detailed fitness measures,” Nayor says, “we hope that our study will provide important information that can ultimately be used to improve physical fitness and overall health across the life course.”
Nayor, a BU School of Medicine assistant professor of medicine, is
also a cardiologist specializing in heart failure at Boston Medical Center,
BU’s primary teaching hospital and the city of Boston’s safety net
hospital. The Brink caught up with Nayor
to explain the results of the study and what people should know about exercise
in relation to fitness.
People
might see a study that finds that moderate to vigorous activity is the best way
to improve fitness, and think, isn’t that obvious? But your research is more
specific than that, so can you tell us what was surprising or perhaps revealing
about your work?
Matthew Nayor: While there is a wealth of evidence supporting the
health benefits of both physical activity and higher levels of fitness, the
actual links between the two are less well understood, especially in the
general population (as opposed to athletes or individuals with specific medical
problems). Our study was designed to address this gap, but we were also
interested in answering several specific questions.
First, we wondered how different intensities of physical activity
might lead to improvements in the body’s responses during the beginning,
middle, and peak of exercise. We expected to find that higher amounts of
moderate-vigorous physical activity, like exercise, would lead to better peak
exercise performance, but we were surprised to see that higher intensity
activity was also more efficient than walking in improving the body’s ability
to start and sustain lower levels of exertion.
We were also uncertain whether the number of steps per day or less
time spent sedentary would truly impact peak fitness levels. We found that they
were associated with higher fitness levels in our study group. These findings
were consistent across categories of age, sex, and health status, confirming
the relevance of maintaining physical activity [throughout the day] for
everyone.
Second, we asked, how do different combinations of the three
activity measures contribute to peak fitness? Intriguingly, we observed that
individuals with higher-than-average steps per day, or moderate-vigorous
physical activity, had higher-than-average fitness levels, regardless of how much time they spent sedentary. So,
it seems that much of the negative effect that being sedentary has on fitness
may be offset by also having higher levels of activity and exercise.
Our third question was, are more recent physical activity habits
more important than previous exercise habits in determining current levels of
fitness? Interestingly, we found that participants with high activity values at
one assessment and low values at another assessment, performed eight years
apart, had equivalent levels of fitness, whether or not the high value
coincided with the fitness testing. This suggests that there may be a “memory
effect” of previous physical activity on current levels of fitness.
A
lot of people wear Fitbits or their Apple Watch to track their daily step
counts these days, and they might think, hey, I did 10,000 steps today! But it
sounds like your research suggests that while walking is valuable, it’s not the
same as exercise?
Well, I think we need to be a little careful with this
interpretation. It is important to note that higher steps were associated with
higher fitness levels in our study, which is reassuring, especially for older
individuals or those with medical conditions that may prohibit higher levels of
exertion. There is also ample evidence from other studies that higher step
counts are associated with a host of favorable health outcomes. So, I would not
want to dissuade people from following their step counts.
However, if your goal is to improve your fitness level, or to slow
down the inescapable decline in fitness that occurs with aging, performing at
least a moderate level of exertion [through intentional exercise] is over three
times more efficient than just walking at a relatively low cadence.
Where
is that line? When does exercise go from moderate to rigorous, for people who
might be wondering if they are doing enough?
We used definitions from prior studies that categorized a cadence
of 60-99 steps/minute as low-level exertion, while 100-129 steps/minute is
generally considered to be indicative of moderate physical activity and greater
than 130 steps/minute is considered vigorous. These step counts may need to be
a bit higher in younger individuals. The Physical Activity Guidelines for Americans
recommend 150-300 minutes/week of moderate intensity or 75-150 minutes/week of
vigorous intensity exercise. However, this upper limit is really a guidance
meant to encourage people to exercise. In our study, we did not observe any
evidence of a threshold beyond which higher levels of activity were no longer
associated with greater fitness.
Can
you explain in some detail how the results of your study were achieved,
studying participants in the Framingham Heart Study?
Thank you for this question and for the opportunity to thank the Framingham Heart Study participants. It is only through their voluntary participation over three generations now that studies such as ours are possible. For our study, we analyzed data from participants of the Third Generation cohort (literally the grandchildren of the original participants, in many cases) and the multiracial sample. At the most recent study visit in 2016–2019, we performed cardiopulmonary exercise tests (CPETs) on stationary cycles for comprehensive fitness evaluations.
CPETs are the “gold standard”
assessment of fitness and involve exercise testing with a face mask or
mouthpiece to measure the oxygen that is breathed in and the carbon dioxide
that’s breathed out during exercise. You may have seen professional endurance
athletes (such as cyclists) performing similar tests during training sessions.
Participants also took home accelerometers, which were worn on belts around
their waist for eight days after their study visit. Accelerometers were worn at
the recent study visit and at the prior visit eight years earlier, and
information was compared.
Do
you have your own exercise routine, where you are consciously thinking of
moderate versus rigorous, and trying to find that balance?
Well, I’m certainly not a competitive athlete, but I try to stay
active. One aspect of our results that I keep coming back to is the finding
that higher levels of sedentary time can be offset by dedicated exercise. I
find this reassuring—especially during the pandemic when many of us are spending
even more time seated in front of a computer—that my daily run or Peloton class
is serving to at least preserve my fitness level.
Reference: “Physical activity and fitness in the community: the
Framingham Heart Study” by Matthew Nayor, Ariel Chernofsky, Nicole L Spartano,
Melissa Tanguay, Jasmine B Blodgett, Venkatesh L Murthy, Rajeev Malhotra,
Nicholas E Houstis, Raghava S Velagaleti, Joanne M Murabito, Martin G Larson,
Ramachandran S Vasan, Ravi V Shah and Gregory D Lewis, 26 August 2021, European Heart Journal.
DOI:
10.1093/eurheartj/ehab580
This research was supported by the National Heart, Lung and Blood
Institute, the National Institutes of Health, the American Heart Association, a
Career Investment Award from the BU School of Medicine’s Department of
Medicine, the Evans Medical Foundation, and the Jay and Louis Coffman Endowment
from BU School of Medicine’s Department of Medicine.
